Overload protection of multiple devices with a single circuit breaker

ABSTRACT

A plurality of circuits or devices which may have different power requirements are protected against small overloads by a single circuit breaker. Overload detectors associated with each of the devices provide a circuit breaker opening signal when excessive current flows to its associated device.

United States Patent l ]3,6ll,076

James Fred Darrow Henrietta, N.Y.

Jan. 27 1970 Oct. 5, 1971 General Electric Company Inventor Appl. No. Filed Patented Assignee 3,302,061 1/1967 Edmunds 317/26 X FOREIGN PATENTS 1,272,846 8/1961 France 317/26 Primary Examiner.l. D. Miller Assistant ExaminerHarvey F endclman AttarneysRaymond H. Quist, Allen E. Amgott, Henry W. Kaufmann, Joseph B. Forman, Frank L. Neuhauser and Oscar B. Waddcll ABSTRACT: A plurality ofcircuits or devices which may have different power requirements are protected against small overloads by a single circuit breaker. Overload detectors associated with each of the devices provide a circuit breaker opening signal when excessive current flows to its associated e es-..

[52] US. Cl 317/33 SC, 307/35, 317/27, 317/46, 317/52 [51] Int. Cl H02h 3/08 [50] Field of Search 317/26, 27, 46,52, 33; 307/30, 35, 86, 125, 126, 130, 131

[56] References Cited UNITED STATES PATENTS 3,171,112 2/1965 Martin 317/46X 22B POWER SUPP LY J I 308 24A 24B 24m i Em N PULSE GENERATOR N26 PATENTEUncI sum $611,076

POWER SUPPI\ Y PULSE GENERATOR \26 INVENTOR.

James F. Darrow ATTORNEY.

OVERLOAD PROTECTION OF MULTIPLE DEVICES WITH A SINGLE CIRCUIT BREAKER BACKGROUND OF THE INVENTION This invention relates generally to current overload protection, and more specifically to a system in which a single circuit breaker provides protection against small current overloads for a plurality of devices.

In many applications a single DC power supply is used as a source or power for a plurality of devices or circuits. It can be seen that a single circuit breaker will not provide protection against small overloads in any one device or circuit without being overly sensitive to fluctuations in power demands. On the other hand, providing separate overload protection for each of the devices complicates the system and increases its cost.

SUMMARY OF THE INVENTION It is an object of this invention to provide protection against small overloads for a plurality of circuits or devices by utilizing a single circuit breaker.

In a preferred form of the invention, each of a plurality of circuits or devices has an associated inductive current monitoring device. An excessive current flowing to one of said circuits induces a current sufficient to cause the circuit breaker to open.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic circuit diagram of the overload protective device of this invention; and

FIG. 2 is a schematic isometric of a current monitoring device which may be employed in practicing the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, DC power supply supplies electrical power through line 12 and feeder lines l2A-l2N to devices or circuits l4A-l4N. Devices l4A-l4N may have equal or different power requirements which may vary from zero up to a maximum permissible load. Thus the total load on power supply 10 may vary substantially from time to time.

Circuit breaker 16 is provided to interrupt current from power supply 10 to line 12 upon the occurrence of a greater than permissible current in any one of feeder lines l2A-l2N, even though the total power on line 12 is within acceptable limits.

Circuit breaker 16 is actuated by passage of current through its coil 18. Controlled rectifier 20 normally prevents current flow through coil I8, but permits such flow when a control current passes through its gate electrode.

In accordance with the invention, the necessary control current may be derived from any one of diodes 22A22N arranged in an OR circuit. Thus circuit breaker 16 will be opened whenever any one of diodes 22A-22N experiences a voltage greater than its forward breakdown voltage.

Overcurrent detectors 24A-2 N driven by pulse generator 26 through lines 28A-28N are connected to diodes 22A-22N by lines 30A-30N. Overcurrent detectors 24A-24N monitor the current in their respective feeder lines l2A-l2N, and are adjusted to supply the control current to controlled rectifier 20 whenever the current being monitored becomes excessive.

Referring to FIG. 2, the structure of overcurrent detector 24A will now be described, it being understood that overcurrent detectors 24B-24N are similar.

Conductor 12A is the branch of power supply line 12 which provides power to device 14A. Surrounding conductor 12A is magnetic core 32. Input coil 34 on core 24 is periodically supplied with a short high intensity pulse by pulse generator 26 through line 28A. This pulse is made sufficiently large to completely magnetize core 32 in the direction indicated by the arrows, and induces a current in output coil 36 in the direction shown. Diode 38 shunted across output coil 36 causes this induced current to circulate throu h the coil.

Conductor 12A is supplying irect current in the direction indicated to device 14A. During the intervals between the pulses in input coil 34, the current in conductor 12A causes flux in core 32 to change in the direction opposite from that indicated by the arrows. The change in flux in core 32 induces a current in output coil 36 which is proportional to the current in conductor 12A, and in a direction opposite to that shown by the arrow. Potentiometer 40 is adjusted to produce a voltage drop such that only when the current in conductor 12A exceeds a desired amount is the induced current large enough to exceed the forward breakdown voltage of diode 22A.

Although a controlled rectifier is employed in the FIG. 1 arrangement, another component having similar characteristics may also be employed. In the same manner, while a particular overcurrent detector is illustrated in FIG. 2, other devices might be employed, see for example the Direct Current Responsive Device described in US. Pat. application Ser. No. 602,909, filed Dec. l9, I966 now US. Pat. No. 3,490,042.

While a particular embodiment of an overload protective circuit has been shown and described, it will be obvious that changes and modifications can be made without departing from the spirit of the invention and the scope of the appended claims.

I claim:

I. In combination with a plurality of circuits or devices receiving power from a single direct current power supply, an overload protective circuit comprising:

a circuit breaker in the common power supply line for said circuits or devices;

detecting means inductively associated with each of the feeder lines supplying power from said common power line to said circuits or devices for detecting an overload in its respective feeder line, and for delivering an output signal indicating an overload;

diodes connected to the outputs of each of said detecting means and arranged in an OR circuit;

means responsive to an overload signal from any one of said diodes for actuating said circuit breaker;

said circuit breaker including a coil connected to said common power supply line; and

a controlled rectifier connected in series with said coil with its gate electrode connected to said OR circuit. 

1. In combination with a plurality of circuits or devices receiving power from a single direct current power supply, an overload protective circuit comprising: a circuit breaker in the common power supply line for said circuits or devices; detecting means inductively associated with each of the feeder lines supplying power from said common power line to said circuits or devices for detecting an overload in its respective feeder line, and for delivering an output signal indicating an overload; diodes connected to the outputs of each of said detecting means and arranged in an OR circuit; means responsive to an overload signal from any one of said diodes for actuating said circuit breaker; said circuit breaker including a coil connected to said common power supply line; and a controlled rectifier connected in series with said coil with its gate electrode connected to said OR circuit. 